The two related oxo-bridged diiron(III) complexes [(phen)2(H2O)Fe-O-Fe(H2O)(phen)2](NO3)4 (1  , phen = 1,10-phenanthroline) and [TPA(H2O)Fe-O-Fe(H2O)TPA](NO3)4 (2  , TPA = tris(2-pyridylmethyl)amine) are shown to abstract hydrogen atoms from 4-hydroxyphenol (hydroquinone) and 4-methylphenol (p-cresol). Quantification of the organic products shows that hydroquinone is oxidized to benzoquinone, while oxidation of p-cresol yields the o,p'-dimer of 4-methylphenoxyl known as Pummerer's ketone. Pummerer's ketone is usually accompanied by an o,o'-biphenyl dimer, which is not observed in this case. Hydrogen atom transfer from phenols is generally faster with 1  than with 2  , and kinetic data on both complexes will be presented. In particular, the clean conversion of p-cresol into Pummerer's ketone allows kinetic analysis of a reaction that is still not well understood nearly 100 years after it's initial discovery.

Oxidation of phenols by (μ-oxo)diiron(III) complexes of 1,10-phenanthroline and tris(2-pyridylmethyl)amine

244th National Meeting (2012)

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